1. Field of the Invention
The invention relates to the field of printing systems, and in particular, to regression testing of printing systems.
2. Discussion of Related Art
The design, manufacture and utilization of printers and printing systems are continually changing. New features implemented in hardware and software for printing systems are being developed to improve the performance of printing systems and to lower costs. During the design and development of new printing systems, and of improvements in existing systems, engineers and scientists must frequently test the effects of new changes on printer output. A diagnostic and quality control method known as regression testing is used to compare outputs from various combinations of hardware and software to determine if a change in an element of the system causes an undesirable change in output of the system. If an undesirable change in the output occurs, the identified error may be used by designers to modify their particular hardware or software to eliminate the undesirable change in system output. Unfortunately, identifying the source or cause of the change in output can be difficult, given the innumerable dependencies between the hardware and software elements of a printing system.
Generally, when a particular type of change is introduced in either software or hardware of the printing system, a single test of the printing system is insufficient to test all the possible effects of the change on printer output. Instead, a collection of various tests, often referred to as a suite of tests, is utilized in regression testing a printing system to test comprehensively the effect of a change. Typically, certain tests are used to test some types of changes, and other tests are used to test other types of changes. Since there are many different possible types of changes that can be made in the hardware and software of a printing system, many different tests must be available to designers to test the effects of the changes.
Regression testing a printing system is further complicated by the task of analyzing output to determine whether undesirable changes have occurred. In any given regression test, a given input to a given printing system is supposed to produce a given expected output. If processing of the given input in a changed printing system produces the expected (standard) output, then the printing system has passed that particular regression test. If the output is different from the expected output, however, then the printing system has failed the regression test. Regression testing a printing system is further complicated, therefore, by the task of analyzing output to determine whether undesirable changes have occurred relative to the expected output. The task of analysis is not always straightforward or easy. Traditionally, output of a printing system being tested is visually compared with a desired standard output produced by an unchanged system. Visual analysis, however, is both tedious and somewhat subjective, making it prone to inaccuracy and unreliability.
Thus, improved techniques are needed to perform efficient regression testing of printing systems, especially during design and development of complex printing systems when many different elements are being changed and tested.